Nanoparticles of Ni1-x Zn (x) Fe2O4 (x = 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0) were synthesized by the sol-gel auto-combustion method using ethylenediamine tetra acetic acid as a complexion agent. The detailed analysis of X-ray diffraction revealed that the crystalline structure was cubic spinel and by increasing x, it underwent a phase transition from normal to inverse spinel. The crystal lattice constant was increased gradually with increasing zinc substitution from 0.8339 nm (x = 0.0) to 0.8443 nm (x = 1.0). Also, the average crystallite size, which is determined from Scherrer formula, was about 14-35 nm. The spinel phase formation was further monitored by the FTIR analysis. The vibration sample magnetometer data showed that by increasing Zn doping level up to x = 0.3, the magnetization was increased and it was decreased by further increase in x. This effect was discussed by metal cations distribution into the tetrahedral and octahedral sites. Also, the coercivity was decreased by increasing Zn content due to the decrease of magnetocrystalline anisotropy constant of the samples.